GM Genuine Parts Brake Drums are designed, engineered, and tested to rigorous standards, and are backed by General Motors. These brake drums are cylinder shaped bowls where the wheel cylinder presses the brake shoes outward against the inside of the drum. Drums are typically found on older vehicles and on the rear axles of trucks and some cars. GM Genuine Parts are the true OE parts installed during the production of or validated by General Motors for GM vehicles. Some GM Genuine Parts may have formerly appeared as ACDelco GM Original Equipment (OE).